Coating Composition for Extreme Washable Coatings

ABSTRACT

A coating composition including: an aqueous dispersion of self-crosslinkable core-shell particles, where the core-shell particles include (1) a polymeric core at least partially encapsulated by (2) a polymeric shell having urethane linkages, keto and/or aldo functional groups, and hydrazide functional groups, where the polymeric core is covalently bonded to at least a portion of the polymeric shell, and an acrylic polymer, where the acrylic polymer is non-reactive with the polymeric core and the polymeric shell. A substrate coated with a coating formed from the coating composition and a method of improving stain resistance of a substrate are also disclosed.

FIELD OF THE INVENTION

The present invention relates to a coating composition having an aqueousdispersion of self-crosslinkable core-shell particles and an acrylicpolymer non-reactive with the core and shell of the core-shellparticles, a substrate coated therewith, and a method of improving stainresistance of a substrate.

BACKGROUND OF THE INVENTION

Aqueous architectural paints, such as those covering interior walls, andother coatings commonly become stained as the result of everyday trafficin the area in which the coating composition was applied. Stainresistance refers to the resistance to stain, difficulty of being wettedby stain, difficulty of being adhered to by stain, and/or easiness ofstain removal without damage to the coating (i.e. washability).

SUMMARY OF THE INVENTION

The present invention relates to a coating composition including: anaqueous dispersion of self-crosslinkable core-shell particles, where thecore-shell particles include (1) a polymeric core at least partiallyencapsulated by (2) a polymeric shell having urethane linkages, ketoand/or aldo functional groups, and hydrazide functional groups, wherethe polymeric core is covalently bonded to at least a portion of thepolymeric shell, and an acrylic polymer, where the acrylic polymer isnon-reactive with the polymeric core and the polymeric shell.

The present invention also relates to a method of improving stainresistance of a substrate including: preparing a coating composition by:preparing an aqueous dispersion of self-crosslinkable core-shellparticles dispersed in an aqueous medium, where the core-shell particlesinclude (1) a polymeric core at least partially encapsulated by (2) apolymeric shell having urethane linkages, keto and/or aldo functionalgroups, and hydrazide functional groups where the polymeric core iscovalently bonded to at least a portion of the polymeric shell; andadding an acrylic polymer to the aqueous dispersion, the acrylicpolymer, where the acrylic polymer is non-reactive with the polymericcore and the polymeric shell; and applying the coating composition to asubstrate.

DESCRIPTION OF THE INVENTION

For the purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances. Further, in this application, the use of “a”or “an” means “at least one” unless specifically stated otherwise. Forexample, “a” coating, “a” core-shell particle, and the like refer to oneor more of any of these items. Also, as used herein, the term “polymer”is meant to refer to prepolymers, oligomers, and both homopolymers andcopolymers. The term “resin” is used interchangeably with “polymer”.

The present invention is directed to a coating composition whichincludes: in addition to an acrylic polymer, an aqueous dispersion ofself-crosslinkable core-shell particles, wherein the core-shellparticles comprise (1) a polymeric core at least partially encapsulatedby (2) a polymeric shell. The polymeric shell comprises: (i) urethanelinkages, (ii) keto and/or aldo functional groups, and (iii) hydrazidefunctional groups. The polymeric core is covalently bonded to at least aportion of the polymeric shell. The coating composition comprises anacrylic polymer. The acrylic polymer is non-reactive with the polymericcore and the polymeric shell.

As used herein, the transitional term “comprising” (and other comparableterms, e.g., “containing” and “including”) is “open-ended” and open tothe inclusion of unspecified matter. Although described in terms of“comprising”, the terms “consisting essentially of” and “consisting of”are also within the scope of the invention.

As used herein, an “aqueous medium” refers to a liquid medium comprisingat least 50 wt % water, based on the total weight of the liquid medium.Such aqueous liquid mediums can for example comprise at least 60 wt %water, or at least 70 wt % water, or at least 80 wt % water, or at least90 wt % water, or at least 95 wt % water, or 100 wt % water, based onthe total weight of the liquid medium. The solvents that, if present,make up less than 50 wt % of the liquid medium include organic solvents.Non-limiting examples of suitable organic solvents include polar organicsolvents, e.g. protic organic solvents such as glycols, glycol etheralcohols, alcohols, volatile ketones, glycol diethers, esters, anddiesters. Other non-limiting examples of organic solvents includearomatic and aliphatic hydrocarbons.

Further, the term “self-crosslinkable” refers to a polymeric particlehaving two or more functional groups that are reactive with each otherand which participate in intramolecular and/or intermolecularcrosslinking reactions to form a covalent linkage in the absence of anyexternal crosslinking agent. For example, the polymeric particles of thepresent invention can each comprise hydrazide functional groups as wellas a keto and/or aldo functional groups that can react with each otherto yield hydrazone linkages. As used herein, a “crosslinking agent”,“crosslinker”, and like terms refers to a molecule comprising two ormore functional groups that are reactive with other functional groupsand which is capable of linking two or more monomers or polymermolecules through chemical bonds. It is appreciated that theself-crosslinkable core-shell particles can also react with separatecrosslinking agents when present.

The aqueous dispersed core-shell particles of the coating compositioninclude a core that is at least partially encapsulated by the shell. Thepolymeric core may be an acrylic core that is partially bonded to apolyurethane/polyurea shell. The shell may include a water dispersiblegroup, so as to be dispersible in the aqueous dispersion. A core-shellparticle in which the core is at least partially encapsulated by theshell refers to a particle comprising (i) at least a first material ormaterials that form the center of the particle (i.e., the core) and (ii)at least a second material or materials (i.e., the shell) that form alayer over at least a portion of the surface of the first material(s)(i.e., the core). It is appreciated that the first material(s) thatforms the core is different from the second material(s) that forms theshell. Further, the core-shell particles can have various shapes (ormorphologies) and sizes. For example, the core-shell particles can havegenerally spherical, cubic, platy, polyhedral, or acicular (elongated orfibrous) morphologies. The core-shell particles can also have an averageparticle size of 30 to 300 nanometers, or from 40 to 200 nanometers, orfrom 50 to 150 nanometers. As used herein, “average particle size”refers to volume average particle size. The average particle size canfor example be determined with a Zetasize 3000HS following theinstructions in the Zetasize 3000HS manual.

The polymeric core typically comprises an addition polymer derived fromethylenically unsaturated monomers. The ethylenically unsaturatedmonomers can comprise a (meth)acrylate monomer, a vinyl monomer, or acombination thereof. As such, the polymeric core can comprise a(meth)acrylate polymer, a vinyl polymer, or a combination thereof. Asused herein, the term “(meth)acrylate” refers to both the methacrylateand the acrylate. Moreover, the backbone, or main chain, of a polymer orpolymers that form at least a portion of the polymeric shell cancomprise urea linkages and/or urethane linkages and may optionallyfurther comprise other linkages. For instance, the polymeric shell cancomprise a polyurethane with a backbone that includes urethane linkagesand urea linkages. As indicated, the polymeric shell can also compriseadditional linkages including, but not limited to, ester linkages, etherlinkages, and combinations thereof.

The polymeric core and/or polymeric shell can also comprise one or more,such as two or more, reactive functional groups. The term “reactivefunctional group” refers to an atom, group of atoms, functionality, orgroup having sufficient reactivity to form at least one covalent bondwith another co-reactive group in a chemical reaction. At least some ofthe reactive functional groups of the polymeric shell are ketofunctional groups (also referred to as ketone functional groups) and/oraldo functional groups (also referred to as aldehyde functional groups)as well as hydrazide functional groups. Optionally, the polymeric corealso comprises reactive functional groups such as keto functionalgroups, aldo functional groups, or combinations thereof. Alternatively,the polymer core is completely free of reactive functional groups suchas keto functional groups and aldo functional groups.

Other non-limiting examples of additional reactive functional groupsthat can be present on the polymeric shell and/or the polymeric coreinclude carboxylic acid groups, amine groups, epoxide groups, hydroxylgroups, thiol groups, carbamate groups, amide groups, urea groups,isocyanate groups (including blocked isocyanate groups), ethylenicallyunsaturated groups, and combinations thereof. As used herein,“ethylenically unsaturated” refers to a group having at least onecarbon-carbon double bond. Non-limiting examples of ethylenicallyunsaturated groups include, but are not limited to, (meth)acrylategroups, vinyl groups, and combinations thereof. It is appreciated thatthe polymeric shell, polymeric core, or both, can be completely free of(i.e., does not contain) any of the additional reactive functionalgroups.

The polymeric core and polymeric shell of the core-shell particles canbe prepared to provide a hydrophilic polymeric shell with enhancedwater-dispersibility/stability and a hydrophobic polymeric core. As usedherein, the term “hydrophilic” refers to polymers, monomers, and othermaterials that have an affinity for water and which will disperse ordissolve in water or other aqueous-based mediums having a pH greaterthan 5 at ambient temperature (20° C-27° C.). Hydrophilic materials,such as hydrophilic polymers, typically have water-dispersible groups. A“water-dispersible group” refers to a group having or formed from one ormore hydrophilic functional groups that have an affinity for water andwhich help disperse a compound, such as a polymer, in water or otheraqueous based mediums. Further, as used herein, the term “hydrophobic”refers to polymers, monomers, and other materials that lack an affinityfor water or other aqueous based mediums and tend to repel, not dissolveor disperse in, and/or not be wetted by water or other aqueous basedmediums. Hydrophobic materials, such as hydrophobic polymers, are oftencompletely free of water-dispersible groups.

As indicated, the polymeric core and polymeric shell of the core-shellparticles can be prepared to provide a hydrophilic polymeric shell withenhanced water-dispersibility/stability and a hydrophobic polymericcore. Thus, the polymeric shell can comprise hydrophilicwater-dispersible groups while the polymeric core can be completely freeof hydrophilic water-dispersible groups. The hydrophilicwater-dispersible groups can increase the water-dispersibility/stabilityof the polymeric shell in the aqueous medium so that the polymeric shellat least partially encapsulates the hydrophobic core.

As previously described, the water-dispersible groups comprise one ormore hydrophilic functional groups. For example, the polymer(s) thatform the hydrophilic polymeric shell can comprise ionic or ionizablegroups such as acid groups like carboxylic acid functional groups orsalts thereof. Carboxylic acid functional group could for example beintroduced by using a carboxylic acid group containing diol to form thepolymeric shell. The acid groups such as carboxylic acid functionalgroups can be at least partially neutralized (i.e., at least 30% of thetotal neutralization equivalent) by an inorganic base, such as avolatile amine, to form a salt group. A volatile amine refers as anamine compound having an initial boiling point of less than or equal to250° C. as measured at a standard atmospheric pressure of 101.3 kPa.Examples of suitable volatile amines are ammonia, dimethylamine,trimethylamine, monoethanolamine, and dimethylethanolamine. It isappreciated that the amines will evaporate during the formation of thecoating to expose the acid groups such as carboxylic acid functionalgroups and allow the acid groups such as carboxylic acid functionalgroups to undergo further reactions such as with a crosslinking agentreactive with the acid groups or carboxylic acid functional groups.Other non-limiting examples of water-dispersible groups includepolyoxyalkylene groups such as by using polyethylene/propylene glycolether materials for example.

In some examples, the polymeric shell is formed from (i) polyurethanescomprising pendant and/or terminal keto and/or aldo functional groups aswell as pendant and/or terminal carboxylic acid functional groups, and(ii) polyurethanes comprising pendant and/or terminal hydrazidefunctional groups as well as pendant and/or terminal carboxylic acidfunctional groups. As previously described, the carboxylic acidfunctional groups can be at least partially neutralized (i.e., at least30% of the total neutralization equivalent) by an inorganic base, suchas a volatile amine, to form a salt group as previously described.Further, the polymeric core can be a hydrophobic core that is completelyfree of such carboxylic acid groups and salt groups formed therefrom. A“pendant group” refers to a group that is an offshoot from the side ofthe polymer backbone and which is not part of the polymer backbone. Incontrast, a “terminal group” refers to a group on an end of the polymerbackbone and which is part of the polymer backbone.

The polymeric shell may include a fluorine-containing group and/or asilicon-containing group bonded to the polymeric shell. Thefluorine-containing group and/or the silicon-containing group may beco-polymerized with the polymeric core and also bonded to the polymericshell. Examples of such fluorine-containing groups and/or asilicon-containing groups include: fluorofunctional acrylate(methacrylate), such as: trideca fluoro octy methacrylate,tridodecafluoro octyl methacrylate, and polydimethyl silicone acrylate(methacrylate) (such as those available in varying molecular weightsfrom Shin-Etsu Chemical (Tokyo, Japan)). The fluorine-containing groupand/or the silicon-containing group may be linearly bonded on thepolymeric shell. Examples of such fluorine-containing group and/or asilicon-containing groups include: ethoxylated polydimethyl siloxane(e.g., SILSURF A008-UP from Siltech Corporation (Toronto, Canada)) andCapstone AL62 from The Chemours Company (Wilmington, Del.). Use offluorine-containing groups and/or the silicon-containing groups mayimprove stain resistance of the coating formed from the coatingcomposition due to their hydrophobic characteristics.

The polymeric shell is also covalently bonded to at least a portion ofthe polymeric core. For example, the polymeric shell can be covalentlybonded to the polymeric core by reacting at least one functional groupon the monomers and/or prepolymers that are used to form the polymericshell with at least one functional group on the monomers and/orprepolymers that are used to form the polymeric core. The functionalgroups can include any of the functional groups previously describedprovided that at least one functional group on the monomers and/orprepolymers that are used to form the polymeric shell is reactive withat least one functional group on the monomers and/or prepolymers thatare used to form the polymeric core. For instance, the monomers and/orprepolymers that are used to form the polymeric shell and polymeric corecan both comprise at least one ethylenically unsaturated group that arereacted with each other to form a chemical bond. As used herein, a“prepolymer” refers to a polymer precursor capable of further reactionsor polymerization by one or more reactive groups to form a highermolecular mass or cross-linked state.

Various components can be used to form the core-shell particles of thepresent invention. For example, the core-shell particles can be formedfrom isocyanate functional polyurethane prepolymers, polyamines,hydrazide functional compounds, and ethylenically unsaturated monomers.The isocyanate functional polyurethane prepolymers can be preparedaccording to any method known in the art, such as by reacting at leastone polyisocyanate with one or more compound(s) having functional groupsthat are reactive with the isocyanate functionality of thepolyisocyanate. Reactive functional groups can be activehydrogen-containing functional groups such as hydroxyl groups, thiolgroups, amine groups, hydrazide groups, and acid groups like carboxylicacid groups. A hydroxyl group may, for example, react with an isocyanategroup to form a urethane linkage. A primary or secondary amine group mayreact with an isocyanate group to form a urea linkage. Examples ofsuitable compounds that can be used to form the polyurethane include,but are not limited to, polyols, polyisocyanates, compounds containingone or more carboxylic acid groups, such as diols containing one or morecarboxylic acid groups, polyamines, hydroxyl functional ethylenicallyunsaturated components, such as hydroxyalkyl esters of (meth)acrylicacid, and/or other compounds having reactive functional groups, such ashydroxyl groups, thiol groups, amine groups, and carboxylic acid groups.The polyurethane prepolymer can also be prepared with keto and/or aldofunctional monoalcohols.

Non-limiting examples of suitable polyisocyanates include isophoronediisocyanate (IPDI), dicyclohexylmethane 4,4′-diisocyanate (H12MDI),cyclohexyl diisocyanate (CHDI), m-tetramethylxylylene diisocyanate(m-TMXDI), p-tetramethylxylylene diisocyanate (p-TMXDI), ethylenediisocyanate, 1,2-diisocyanatopropane, 1,3 -diisocyanatopropane,1,6-diisocyanatohexane (hexamethylene diisocyanate or HDI), 1,4-butylenediisocyanate, lysine diisocyanate, 1,4-methylene bis-(cyclohexylisocyanate), toluene diisocyanate (TDI), m-xylylenediisocyanate (MXDI)and p-xylylenediisocyanate, 4-chloro-1,3-phenylene diisocyanate,1,5-tetrahydro-naphthalene diisocyanate, 4,4′-dibenzyl diisocyanate, and1,2,4-benzene triisocyanate, xylylene diisocyanate (XDI), and mixturesor combinations thereof.

Examples of polyols that can be used to prepare a polyurethane basedpolymer such as the polyurethane prepolymer include, but are not limitedto, lower molecular weight glycols (less than 5,000 number averagemolecular weight (Mn)), polyether polyols, polyester polyols, copolymersthereof, and combinations thereof. As reported herein, Mn is measured bygel permeation chromatography using a polystyrene standard according toASTM D6579-11 (performed using a Waters 2695 separation module with aWaters 2414 differential refractometer (RI detector); tetrahydrofuran(THF) was used as the eluent at a flow rate of 1 ml/min, and two PLgelMixed-C (300×7.5 mm) columns were used for separation at the roomtemperature; weight and number average molecular weight of polymericsamples can be measured by gel permeation chromatography relative tolinear polystyrene standards of 800 to 900,000 Da) Non-limiting examplesof low molecular weight glycols include ethylene glycol, diethyleneglycol, triethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol,tetramethylene glycol, hexamethylene glycol, and combinations thereof,as well as other compounds that comprise two or more hydroxyl groups andcombinations of any of the foregoing. Non-limiting examples of suitablepolyether polyols include polytetrahydrofuran, polyethylene glycol,polypropylene glycol, polybutylene glycol, and combinations thereof.Non-limiting examples of polyester polyols include those prepared from apolyol comprising an ether moiety and a carboxylic acid or anhydride.

Other suitable polyols include, but are not limited to,cyclohexanedimethanol, 2-ethyl-1,6-hexanediol, 1,3-propanediol,1,4-butanediol, neopentyl glycol, trimethylol propane, 1,2,6-hexantriol,glycerol, and combinations thereof. Further, suitable amino alcoholsthat can be used include, but are not limited to, ethanolamine,propanolamine, butanolamine, and combinations thereof.

Suitable carboxylic acids, which can be reacted with the polyols to forma polyester polyol, include, but are not limited to, diacids such asglutaric acid, succinic acid, malonic acid, oxalic acid, phthalic acid,isophthalic acid, hexahydrophthalic acid, adipic acid, maleic acid, andmixtures thereof. Further, non-limiting examples of acid containingdiols include, but are not limited to, 2,2-bis(hydroxymethyl)propionicacid, which is also referred to as dimethylolpropionic acid (DMPA),2,2-bis(hydroxymethyl)butyric acid, which is also referred to asdimethylol butanoic acid (DMBA), diphenolic acid, and combinationsthereof.

Non-limiting examples of hydrazide functional materials that can be usedin the preparation of the polyurethane prepolymer and to providehydrazide functionality include dihydrazide functional compounds suchas, but not limited to, maleic dihydrazide, fumaric dihydrazide,itaconic dihydrazide, phthalic dihydrazide, isophthalic dihydrazide,terephthalic dihydrazide, trimellitic trihydrazide, oxalic dihydrazide,adipic acid dihydrazide, sebacic dihydrazide, and combinations thereof.

Examples of keto functional monoalcohols that can be used in thepreparation of the polyurethane prepolymer and to provide keto and/oraldo functionality include, but are not limited to, hydroxyacetone,4-hydroxy-2-butanone, 5-hydroxy-4-octanone,4-hydroxy-4-methylpentan-2-one, which is also referred to as diacetonealcohol, 3-hydroxyacetophenone, and combinations thereof. Further,non-limiting examples of aldo functional monoalcohols includeDL-lactaldehyde solution, 3-hydroxy-butanal, 4-hydroxy-pentanal,5-hydroxy-hexanal, 5-hydroxy-5-methylhexanal,4-hydroxy-4-methyl-pentanal, 3-hydroxy-3-methylbutanal, and combinationsthereof.

Non-limiting examples of compounds, which can be used to incorporateethylenically unsaturated moieties to the polyurethane prepolymer,include hydroxyalkyl esters of (meth)acrylic acid such as hydroxymethyl(meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl (meth)acrylate, and combinations thereof.

The components that form the polyurethane prepolymer can be reacted in astepwise manner, or they can be reacted simultaneously. For example, thepolyurethane prepolymer can be formed by reacting a diisocyanate, apolyol, a carboxyl group-containing diol, a hydroxyl group-containingethylenically unsaturated monomer, and a dihydrazide functionalcompound.

As previously mentioned, the core-shell particles can also be preparedwith polyamines and ethylenically unsaturated monomers not incorporatedinto the polyurethane during preparation thereof. For instance, theisocyanate functional polyurethane prepolymers can be prepared asdescribed above and then reacted with polyamines as a chain extender. Asused herein, a “chain extender” refers to a lower molecular weight(compound having a Mn less than 1,000) compound having two or morefunctional groups that are reactive towards isocyanate.

Suitable polyamines that can be used to prepare the polyurethane basedpolymer include aliphatic and aromatic compounds, which comprise two ormore amine groups selected from primary and secondary amine groups.Examples include, but are not limited to, diamines such as, for example,ethylenediamine, hexamethylenediamine, 1,2-propanediamine,2-methyl-1,5-penta-methylenediamine, 2,2,4-trimethyl-1,6-hexanediamine,isophoronediamine, diaminocyclohexane, xylylenediamine,1,12-diamino-4,9-dioxadodecane, and combinations thereof. Suitablepolyamines are also sold by Huntsman Corporation (The Woodlands, Tex.)under the trade name JEFFAMINE, such as JEFFAMINE D-230 and JEFFAMINED-400.

Other non-limiting examples of suitable polyamine functional compoundsinclude the Michael addition reaction products of a polyamine functionalcompound, such as a diamine, with keto and/or aldo containingethylenically unsaturated monomers. The polyamine functional compoundtypically comprises at least two primary amino groups (i.e., afunctional group represented by the structural formula —NH₂), and theketo and/or aldo containing unsaturated monomers include, but are notlimited to, (meth)acrolein, diacetone (meth)acrylamide, diacetone(meth)acrylate, acetoacetoxyethyl (meth)acrylate, vinyl acetoacetate,crotonaldehyde, 4-vinylbenzaldehyde, and combinations thereof. Theresulting Michael addition reaction products can include a compound withat least two secondary amino groups (i.e., a functional grouprepresented by the structural formula —NRH in which R is ahydrocarbonyl) and at least two keto and/or aldo functional groups. Itis appreciated that the secondary amino groups will react with theisocyanate functional groups of the polyurethane prepolymers to formurea linkages and chain extend the polyurethanes. Further, the ketoand/or aldo functional groups will extend out from the backbone of thechain-extended polyurethane, such as from the nitrogen atom of the urealinkage, for example, to form a polyurethane with pendant keto and/oraldo functional groups.

As indicated, and in accordance with the present invention, the aqueousdispersion includes core-shell particles that have a polymeric shellcomprising keto and/or aldo functional groups as well as hydrazidefunctional groups. The polymeric shell of such core-shell particles canbe prepared with hydrazide functional polymers and keto and/or aldofunctional polymers or polymers that contain both hydrazidefunctionality and keto and/or aldo functionality. The polymers can alsoinclude additional functional groups as previously described including,but not limited to, ethylenically unsaturated groups. For example, thepolymeric shell of such core-shell particles can be prepared with: (i) afirst polyurethane comprising urethane linkages, water-dispersiblegroups such as carboxylic acid groups, ethylenically unsaturated groups,and hydrazide groups; and (ii) a second polyurethane comprising urethanelinkages, water-dispersible groups such as carboxylic acid groups,ethylenically unsaturated groups, keto and/or aldo groups, and,optionally, urea linkages.

Moreover, the first and second polyurethanes can be prepared with thepreviously described components. For instance, the first polyurethanecan be prepared by reacting an isocyanate and ethylenically unsaturatedfunctional polyurethane with a dihydrazide functional compound such asadipic acid dihydrazide. The second polyurethane can be prepared, forexample, by reacting and chain extending isocyanate and ethylenicallyunsaturated functional polyurethanes with the Michael addition reactionproduct of a diamine and keto and/or aldo containing ethylenicallyunsaturated monomers. The isocyanate and ethylenically unsaturatedfunctional polyurethanes used to form the first and second polyurethanescan be formed from polyols, polyisocyanates, diols containing carboxylicacid functionality, and hydroxyl functional ethylenically unsaturatedcomponents.

After forming the polyurethane(s) (for example, the first and secondpolyurethanes previously described), the polyurethane(s) and additionalethylenically unsaturated monomers can be subjected to a polymerizationprocess to form the core-shell particles. The additional ethylenicallyunsaturated monomers can be added after forming the polyurethane(s).Alternatively, the additional ethylenically unsaturated monomers can beused as a diluent during preparation of the polyurethane(s) and notadded after formation of the polyurethane(s). It is appreciated thatethylenically unsaturated monomers can be used as a diluent duringpreparation of the polyurethane(s) and also added after formation of thepolyurethane(s).

The additional ethylenically unsaturated monomers can comprisemulti-ethylenically unsaturated monomers, mono-ethylenically unsaturatedmonomers, or combinations thereof. A “mono-ethylenically unsaturatedmonomer” refers to a monomer comprising only one ethylenicallyunsaturated group, and a “multi-ethylenically unsaturated monomer”refers to a monomer comprising two or more ethylenically unsaturatedgroups.

Non-limiting examples of ethylenically unsaturated monomers include, butare not limited to, alkyl esters of (meth)acrylic acid, hydroxyalkylesters of (meth)acrylic acid, acid group containing ethylenicallyunsaturated monomers, vinyl aromatic monomers, aldo or keto containingethylenically unsaturated monomers, and combinations thereof.

Non-limiting examples of alkyl esters of (meth)acrylic acid includemethyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate,isobutyl (meth)acrylate, ethylhexyl (meth)acrylate, lauryl(meth)acrylate, octyl (meth)acrylate, glycidyl (meth)acrylate, isononyl(meth)acrylate, isodecyl (meth)acrylate, vinyl (meth)acrylate,acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate, andcombinations thereof. Other non-limiting examples includedi(meth)acrylate alkyl diesters formed from the condensation of twoequivalents of (meth)acrylic acid such as, for example, ethylene glycoldi(meth)acrylate. Di(meth)acrylate alkyl diesters formed from C₂₋₂₄diols such as butane diol and hexane diol can also be used.

Non-limiting examples of hydroxyalkyl esters of (meth)acrylic acid andketo and aldo containing ethylenically unsaturated monomers include anyof those previously described. Non-limiting examples of acid groupcontaining ethylenically unsaturated monomers include (meth)acrylicacid, itaconic acid, maleic acid, fumaric acid, crotonic acid, asparticacid, malic acid, mercaptosuccinic acid, and combinations thereof.

Non-limiting examples of vinyl aromatic monomers include styrene,2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, vinylnaphthalene, vinyl toluene, divinyl aromatic monomers, such as divinylbenzene, and combinations thereof.

As previously noted, the ethylenically unsaturated monomers can bepolymerized in the presence of the polyurethane(s), which can alsocontain ethylenically unsaturated groups, to form the core-shellparticles. The polymerization can be conducted using art recognizedtechniques as well as conventional additives such as emulsifiers,protective colloids, free radical initiators, and chain transfer agentsknown in the art.

Thus, in some examples, the core-shell particles of the presentinvention are prepared with: (i) ethylenically unsaturated monomers;(ii) a first polyurethane comprising urethane linkages, carboxylic acidgroups, ethylenically unsaturated groups, and hydrazide groups; and(iii) a second polyurethane comprising urethane linkages, urea linkages,carboxylic acid groups, ethylenically unsaturated groups, and ketoand/or aldo groups. The resulting core-shell particles then comprise apolymeric core prepared from ethylenically unsaturated monomers, thusfor example comprising an addition polymer formed by free radicalpolymerization from a monomer component that may comprise any of theethylenically unsaturated monomers previously mentioned, that iscovalently bonded to at least a portion of a polyurethane shell havingpendant carboxylic acid functional groups, pendant or terminal ketoand/or aldo functional groups, hydrazide functional groups, urethanelinkages, and urea linkages. For enhancedwater-dispersibility/stability, the carboxylic acid functional groups onthe polymeric shell can be at least partially neutralized (i.e., atleast 30% of the total neutralization equivalent) by an inorganic base,such as a volatile amine, to form a salt group as previously described.The polymeric core can also include pendant and/or terminal functionalgroups, such as keto and/or aldo functional groups, by usingethylenically unsaturated monomers that contain additional functionalgroups such as acid group containing ethylenically unsaturated monomersand/or aldo or keto containing ethylenically unsaturated monomers asindicated above. Alternatively, the polymeric core can be completelyfree of additional functional groups such as completely free of ketoand/or aldo functional groups. Further, the polymeric core is covalentlybonded to at least a portion of the polymeric shell after polymerizationof the monomers and polyurethane(s).

The polymeric core of the core-shell particle may have a Tg of from 0°C. to 50° C., such as from 0° C. to 40° C., from 20° C. to 40° C., from20° C. to 30° C., from 30° C. to 50° C., from 30° C. to 40° C., or from40° C. to 50° C., as measured by differential scanning calorimetryaccording to ASTM D3418-15. The Tg referred to in this paragraph refersto the Tg of the polymeric core of the core-shell particle beforeencapsulation by the polymeric shell.

It is appreciated that the core-shell particles described herein aredispersed in an aqueous medium to form a latex. As used herein, a“latex”, with respect to the aqueous dispersed core-shell particles,refers to an aqueous colloidal dispersion of polymeric particles.

In addition to the above-described aqueous dispersion ofself-crosslinkable core-shell particles, the coating compositionincludes an acrylic polymer prepared from an acrylic monomer. Suitableacrylic monomers for forming the acrylic polymer include t-butylaminomethyl (meth)acrylate, (meth)acrylic acid, methyl (meth)acrylate, ethyl(meth)acrylate, butyl (meth)acrylate, hydroxyethyl (meth)acrylate,hydroxybutyl (meth)acrylate, hydroxypropyl (meth)acrylate orcombinations thereof. The acrylic polymer is non-reactive with thepolymeric core and polymeric shell of the self-crosslinkable core-shellparticles. The acrylic polymer may be added to the aqueous dispersionafter the formation of the self-crosslinkable core-shell particles.

The coating composition including the self-crosslinkable core-shellparticles and the acrylic polymer may include the self-crosslinkablecore-shell particles in an amount of at least 10 wt %, at least 20 wt %,at least 30 wt %, or at least 40 wt % of the resin blend, based on totalresin solids weight. The self-crosslinkable core-shell particles caninclude up to 50 wt %, up to 40 wt %, up to 30 wt %, or up to 20 wt % ofthe resin blend, based on total resin solids weight. Theself-crosslinkable core-shell particles can also include a range such asfrom 10 to 50 wt %, or from 10 to 40 wt %, or from 20 to 30 wt %, orfrom 20 to 50 wt %, or from 20 to 40 wt %, or from 30 to 50 wt %, orfrom 30 to 40 wt %, or from 40 to 50 wt % of the resin blend, based ontotal resin solids weight.

The coating composition including the self-crosslinkable core-shellparticles and the acrylic polymer may include the acrylic polymer in anamount of at least 50 wt %, at least 60 wt %, at least 70 wt %, or atleast 80 wt % of the resin blend, based on total resin solids weight.The acrylic polymer can include up to 90 wt %, up to 80 wt %, up to 70wt %, or up to 60 wt % of the resin blend, based on total resin solidsweight. The acrylic polymer can also include a range such as from 50 to90 wt %, or from 50 to 80 wt %, or from 50 to 70 wt %, or from 50 to 60wt %, or from 60 to 90 wt %, or from 60 to 80 wt %, or from 60 to 70 wt%, or from 70 to 90 wt %, or from 70 to 80 wt %, or from 80 to 90 wt %of the resin blend, based on total resin solids weight.

The coating composition may optionally also comprise additionalcomponents. For example, the coating composition can also comprisenon-self-crosslinkable core-shell particles. As used herein,“non-self-crosslinkable” refers to a polymeric particle having one ormore functional groups that are not reactive with each other and whichthus requires one or more external crosslinking agents to undergo acrosslinking reaction. The non-self-crosslinkable core-shell particlescan for example include a polymeric core comprising: (i) residues fromethylenically unsaturated monomers such as (meth)acrylate monomers,vinyl monomers, or a combination thereof and therefore comprise anaddition polymer such as a (meth)acrylate polymer, a vinyl polymer, or acombination thereof; and (ii) keto and/or aldo functional groups.Moreover, the backbone or main chain of the polymer(s) that forms atleast a portion of the polymeric shell can comprise urethane linkagesand, optionally, other linkages such as for example ester linkages,ether linkages, and combinations thereof. Thus, the polymeric core cancomprise keto and/or aldo functional groups, and the polymeric shell cancomprise a polyurethane(s) that is completely free of keto and/or aldofunctional groups and, optionally, completely free of urea linkages.Further, both the polymeric core and the polymeric shell may becompletely free of hydrazide functional groups. It is appreciated thatsuch non-self-crosslinkable core-shell particles can be prepared withsimilar materials as described above with respect to theself-crosslinkable core-shell particles.

The non-self-crosslinkable core-shell particles can also include apolymeric core comprising an addition polymer such as a (meth)acrylatepolymer, a vinyl polymer, or a combination thereof that is derived fromethylenically unsaturated monomers such as (meth)acrylate monomers,vinyl monomers, or a combination thereof, and a polymeric shellcomprising urethane linkages, water-dispersible groups such ascarboxylic acid groups, ethylenically unsaturated groups, keto and/oraldo groups, and, optionally, urea linkages. Moreover, the backbone ormain chain of the polymer(s) that forms at least a portion of thepolymeric shell can, optionally, comprise other linkages such as esterlinkages, ether linkages, and combinations thereof. The resultingcore-shell particles then comprise a polymeric core prepared fromethylenically unsaturated monomers that is covalently bonded to at leasta portion of a polyurethane shell having pendant carboxylic acidfunctional groups, pendant or terminal keto and/or aldo functionalgroups, urethane linkages, and, optionally, urea linkages. For enhancedwater-dispersibility/stability, the carboxylic acid functional groups onthe polymeric shell can be at least partially neutralized (i.e., atleast 30% of the total neutralization equivalent) by an inorganic base,such as a volatile amine, to form a salt group as previously described.The polymeric core can also include pendant and/or terminal functionalgroups, such as keto and/or aldo functional groups, by usingethylenically unsaturated monomers that contain additional functionalgroups as discussed above with respect to the self-crosslinkablecore-shell particles. Alternatively, the polymeric core can becompletely free of additional functional groups such as keto and/or aldofunctional groups. Further, both the polymeric core and the polymericshell can be completely free of hydrazide functional groups. It isappreciated that such core-shell particles can be prepared with similarmaterials as described above with respect to the self-crosslinkablecore-shell particles.

The non-self-crosslinkable core-shell particles can comprise at least0.1 wt %, at least 1 wt %, at least 2 wt %, at least 5 wt %, or at least10 wt % of the resin blend, based on total resin solids weight. Thenon-self-crosslinkable core-shell particles can comprise up to 40 wt %,up to 30 wt %, or up to 20 wt % of the resin blend, based on total resinsolids weight. The non-self-crosslinkable core-shell particles can alsocomprise a range such as from 0.1 to 40 wt %, or from 1 to 30 wt %, orfrom 2 to 20 wt % of the resin blend, based on total resin solidsweight.

The coating composition can also comprise one or more crosslinkers. Forinstance, the coating composition according to the present invention maycomprise at least one crosslinker that is reactive with thefunctionality on the non-self crosslinkable core-shell particlesdescribed above and/or the optional additional film-forming resinsfurther described herein. Non-limiting examples of crosslinkers includepolyhydrazides, carbodiimides, polyols, phenolic resins, epoxy resins,beta-hydroxy (alkyl) amide resins, hydroxy (alkyl) urea resins,oxazolines, alkylated carbamate resins, (meth)acrylates, isocyanates,blocked isocyanates, polyacids, anhydrides, organometallicacid-functional materials, polyamines, polyamides, aminoplasts,aziridines, and combinations thereof.

The crosslinker(s) can react with the core-shell particles to help curethe coating composition. The terms “curable”, “cure”, and the like, meanthat at least a portion of the resinous materials in a composition iscrosslinked or crosslinkable. Cure, or the degree of cure, can bedetermined by dynamic mechanical thermal analysis (DMTA) using a PolymerLaboratories MK III DMTA analyzer conducted under nitrogen. The degreeof cure can for example be at least 10%, such as at least 30%, such asat least 50%, such as at least 70%, or at least 90% of completecrosslinking as determined by the analysis mentioned above.

Further, curing can occur at ambient conditions, with heat, or withother means such as actinic radiation. “Ambient conditions” as usedherein refers to the conditions of the surrounding environment such asthe temperature, humidity, and pressure of the room or outdoorenvironment. For example, the coating composition can be cured atambient room temperature (20° C-27° C.). Further, the term “actinicradiation” refers to electromagnetic radiation that can initiatechemical reactions. Actinic radiation includes, but is not limited to,visible light, ultraviolet (UV) light, infrared and near-infraredradiation, X-ray, and gamma radiation.

The coating composition can comprise at least one crosslinker that isreactive with: (i) the keto and/or aldo functional groups or thehydrazide functional groups on the polymeric shell of theself-crosslinkable core-shell particles; and/or (ii) the keto and aldofunctional groups on the polymeric core and/or shell of thenon-self-crosslinkable core-shell particles when present. Thecrosslinker can also react with functional groups such as keto and aldofunctional groups that can be present on the polymeric core of theself-crosslinkable core-shell particles. For instance, the coatingcomposition can comprise a polyhydrazide that is reactive with the ketoand/or aldo functional groups on the polymeric shell of thenon-self-crosslinkable core-shell particles and keto and/or aldofunctional groups on the polymeric shell of the self-crosslinkablecore-shell particles. The polyhydrazides can include non-polymericpolyhydrazides, polymeric polyhydrazides, or combinations thereof.Non-limiting examples of suitable non-polymeric polyhydrazides includethe dihydrazide functional compounds previously described.

The polymeric polyhydrazides can include various types of polymerscomprising two or more hydrazide functional groups. For example, thepolymeric polyhydrazide can comprise a polyurethane having two or morehydrazide groups. The polyhydrazide functional polyurethane can beprepared by first forming a water-dispersible isocyanate functionalpolyurethane prepolymer. Such water-dispersible isocyanate functionalpolyurethane prepolymers can for example be prepared by reactingpolyols, isocyanates, and, optionally, compounds containing carboxylicacids such as diols containing carboxylic acid groups, and/orpolyamines. Non-limiting examples of these compounds include any ofthose previously described with respect to the polyurethane prepolymerof the core-shell particles.

It is appreciated that the isocyanate functional polyurethane prepolymerused to prepare the polyhydrazide functional polyurethane can includeadditional functional groups. For instance, the isocyanate functionalpolyurethane prepolymer can also include any of the reactive functionalgroups previously described such as carboxylic acid groups that can beat least partially neutralized by an inorganic base to form a salt groupand enhance the water-dispersibility/stability of the polyurethane. Thepolyurethane prepolymer can also be completely free of any of theadditional functional groups. Further, the isocyanate functionalpolyurethane prepolymer can include additional linkages other thanurethanes including, but not limited to, ether linkages, ester linkages,urea linkages, and any combination thereof.

After forming the water-dispersible isocyanate functional polyurethaneprepolymer, the polyurethane prepolymer is reacted with one or morehydrazine and/or polyhydrazide compound(s) to form a water-dispersiblepolyhydrazide functional polyurethane. The hydrazine and polyhydrazidecompounds can also chain extend the isocyanate functional polyurethaneprepolymer. Non-limiting examples of polyhydrazide compounds that can bereacted with the isocyanate functional polyurethane prepolymer includeany of the non-polymeric hydrazide functional compounds previouslydescribed.

The polymeric polyhydrazides can also comprise core-shell particlescomprising a polymeric core at least partially encapsulated by apolymeric shell having two or more hydrazide functional groups. Thepolyhydrazide functional core-shell particles can be prepared byreacting polyurethane prepolymers having isocyanate and ethylenicallyunsaturated functional groups with hydrazine and/or polyhydrazidecompounds and ethylenically unsaturated monomers and/or polymers. Insome examples, the polyhydrazide functional core-shell particles areprepared by reacting polyurethane prepolymers having isocyanate andethylenically unsaturated groups with hydrazine and/or polyhydrazidecompounds to form polyurethanes having hydrazide and ethylenicallyunsaturated groups. The polyurethanes having hydrazide and ethylenicallyunsaturated groups are then polymerized in the presence of ethylenicallyunsaturated monomers and/or polymers to form the core-shell particles.The resulting core-shell particles will comprise a polymeric coreprepared from ethylenically unsaturated monomers and/or polymers thatare covalently bonded to at least a portion of a polyurethane shellhaving hydrazide functional groups and urethane linkages. The polymericshell can also comprise additional functional groups (for example,carboxylic acid functional groups) and/or linkages (for example, esterlinkages and/or ether linkages) as previously described with respect topolyurethane shells. The hydrazide functional core-shell particles canbe also completely free of additional functional groups and linkagessuch as any of those previously described herein. It is appreciated thatthe hydrazide functional core-shell particles that can be used as acrosslinker are completely free of keto and aldo functional groups.

The coating composition can also comprise at least two different typesof crosslinkers that are reactive with the functional groups that may bepresent on the core-shell particles such as keto and/or aldo functionalgroups, hydrazide groups and/or carboxylic acid functional groups. Insome examples, the coating composition comprises a polyhydrazidereactive with the keto and/or aldo functional group, such as any ofthose previously described, and a carbodiimide reactive with carboxylicacid functional groups. Non-limiting examples of suitable carbodiimidesare described in U.S. Patent Application Publication No. 2011/0070374 atparagraphs [0006] to [0105], which is incorporated by reference herein.

In addition, the coating composition can comprise additional materialsincluding, but not limited to, additional resins such as additionalfilm-forming resins. As used herein, a “film-forming resin” refers to aresin that when used in a coating composition can form a self-supportingcontinuous film on at least a horizontal surface through dehydrationand/or upon curing. The term “dehydration” refers to the removal ofwater and/or other solvents. It is appreciated that dehydration can alsocause at least partial curing of a resinous material such as thecore-shell particles and additional resins described herein. The coatingcomposition comprising the additional resin can be dehydrated and/orcured at ambient conditions, with heat, or with other means such asactinic radiation as previously described.

The additional resin can include any of a variety of thermoplasticand/or thermosetting film-forming resins known in the art. The term“thermosetting” refers to resins that “set” irreversibly upon curing orcrosslinking, wherein the polymer chains of the resins are joinedtogether by covalent bonds. Once cured or crosslinked, a thermosettingresin will not melt upon the application of heat and is insoluble insolvents. As noted, the film-forming resin can also include athermoplastic film-forming resin. The term “thermoplastic” refers toresins that are not joined by covalent bonds and, thereby, can undergoliquid flow upon heating and can be soluble in certain solvents.

Non-limiting examples of suitable additional resins includepolyurethanes other than those previously described, polyesters such aspolyester polyols, polyamides, polyethers, polysiloxanes,fluoropolymers, polysulfides, polythioethers, polyureas, (meth)acrylicresins, epoxy resins, vinyl resins, and combinations thereof. Theadditional resins can also include non-particulate resins.

The additional resin can have any of a variety of reactive functionalgroups including, but not limited to, carboxylic acid groups, aminegroups, epoxide groups, hydroxyl groups, thiol groups, carbamate groups,amide groups, urea groups, isocyanate groups (including blockedisocyanate groups), (meth)acrylate groups, and combinations thereof.Thermosetting coating compositions typically comprise a crosslinker thatmay be selected from any of the crosslinkers known in the art to reactwith the functionality of the resins used in the coating compositions.The crosslinkers can include any of those previously described.Alternatively, a thermosetting film-forming resin can be used havingfunctional groups that are reactive with themselves; in this manner,such thermosetting resins are self-crosslinking.

The coating composition can also include other additional materials suchas a colorant. As used herein, “colorant” refers to any substance thatimparts color and/or other opacity and/or other visual effect to thecomposition. The colorant can be added to the coating in any suitableform, such as discrete particles, dispersions, solutions, and/or flakes.A single colorant or a mixture of two or more colorants can be used inthe coatings of the present invention.

Example colorants include pigments (organic or inorganic), dyes, andtints, such as those used in the paint industry and/or listed in the DryColor Manufacturers Association (DCMA), as well as special effectcompositions. A colorant may include, for example, a finely dividedsolid powder that is insoluble, but wettable, under the conditions ofuse. A colorant can be organic or inorganic and can be agglomerated ornon-agglomerated. Colorants can be incorporated into the coating by useof a grind vehicle, such as an acrylic grind vehicle, the use of whichwill be familiar to one skilled in the art.

Example pigments and/or pigment compositions include, but are notlimited to, carbazole dioxazine crude pigment, azo, monoazo, diazo,naphthol AS, salt type (flakes), benzimidazolone, isoindolinone,isoindoline and polycyclic phthalocyanine, quinacridone, perylene,perinone, diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone,anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, dioxazine,triarylcarbonium, quinophthalone pigments, diketo pyrrolo pyrrole red(“DPPBO red”), titanium dioxide, carbon black, and mixtures thereof. Theterms “pigment” and “colored filler” can be used interchangeably.

Example dyes include, but are not limited to, those that are solventand/or aqueous based such as phthalo green or blue, iron oxide, andbismuth vanadate.

Example tints include, but are not limited to, pigments dispersed inwater-based or water miscible carriers such as AQUA-CHEM 896commercially available from Evonik Industries (Essen, Germany), CHARISMACOLORANTS and MAXITONER INDUSTRIAL COLORANTS commercially available fromAccurate Dispersions Division of Eastman Chemical, Inc. (Kingsport,Tenn.).

The colorant which can be used with the coating composition of thepresent invention can also comprise a special effect composition orpigment. As used herein, a “special effect composition or pigment”refers to a composition or pigment that interacts with visible light toprovide an appearance effect other than, or in addition to, a continuousunchanging color. Example special effect compositions and pigmentsinclude those that produce one or more appearance effects such asreflectance, pearlescence, metallic sheen, texture, phosphorescence,fluorescence, photochromism, photosensitivity, thermochromism,goniochromism, and/or color-change. Non-limiting examples of specialeffect compositions can include transparent coated mica and/or syntheticmica, coated silica, coated alumina, aluminum flakes, a transparentliquid crystal pigment, a liquid crystal coating, and combinationsthereof.

The coating composition may include a rheology modifier to adjust theviscosity of the coating composition to a desired level. The rheologymodifier may be a non-associative rheology modifier, such as aninorganic additive (e.g., clays) and hydroxyethyl cellulose (HEC). Therheology modifier may be an associative rheology modifier, such as ahydrophobically-modified ethylene oxide based urethane (HEUR) or ahydrophobically-modified alkali soluble emulsion (HASE). In somenon-limiting examples, the coating composition may have a Stormerviscosity between 80-120 KU (as measured according to ASTM D562) and/oran ICI viscosity between 0.5-5 P (as measured according to ASTM D4287).

The coating composition may include a matting agent. The matting agentmay include inorganic and/or organic matting agents. Suitable inorganicmatting agents include silica, alumina silicate and/or calciumcarbonate, with particle size less than 100 microns, such as below 10microns, as measured using a SEDIGRAPH particle size analyzer fromMicrometrics (Norcross, Ga.). Suitable organic matting agents include awax, a thermoplastic polymer and/or a thermoset polymer, wherein theorganic matting agent is different from the self-crosslinkablecore-shell particles and the acrylic polymer. The matting agents shouldbe present in the coating composition in an amount sufficient to conferlow gloss to the coating, where low gloss is defined as Master PaintersInstitute (MPI) Gloss Levels 1 through 3 (matte finish, velvet-likefinish, and eggshell finish, respectively) with a 60° gloss below 20units and a 85° sheen below 35 units. This gloss value may be measuredusing a micro-TRI-gloss meter from BYK Gardner according to ASTM D523.In some examples, the pigment volume concentration (PVC) of the coatingcomposition may be at least 35%, such as at least 50%.

Other non-limiting examples of further materials that can optionally beused with the coating composition of the present invention includeplasticizers, abrasion resistant particles, anti-oxidants, hinderedamine light stabilizers, UV light absorbers and stabilizers,surfactants, flow and surface control agents, thixotropic agents,catalysts, reaction inhibitors, and other customary auxiliaries.Depending on the volatile organic compounds (VOC) of such additionalcomponents, (particularly coalescing agents and/or plasticizers), thecoating composition of the present invention may contain little or noVOC, such as below 50 g/L or below 25 g/L or below 5 g/L or none.

The coating composition of the present invention, when applied to asubstrate and dried to form a coating, may improve stain resistance ofthe coating compared to the same coating composition that does notinclude the self-crosslinkable core-shell particles. Stain resistance isdefined based on the stain resistance test method described in the belowexamples.

The present invention is also directed to a method of improving stainresistance of a substrate with the coating composition described herein.The method includes applying the coating composition described hereinover at least a portion of the substrate. The coating composition can beapplied in liquid form and dried, such as at temperature conditions inthe range of −10° C. to 50° C.

Formulation of the coating composition involves the process of selectingand admixing appropriate coating ingredients in the correct proportionsto provide a paint with specific processing and handling properties, aswell as a final dry paint film with the desired properties. The coatingcomposition may be applied to a substrate by conventional applicationmethods such as, for example, brushing, roller application, and sprayingmethods such as, for example, air-atomized spray, air-assisted spray,airless spray, high volume low pressure spray, and air-assisted airlessspray. Suitable substrates include, but are not limited to,architectural substrates, such as metallic or non-metallic substratesincluding: concrete, cement board, MDF (medium density fiberboard) andparticle board, gypsum board, wood, stone, metal, plastics, wall paper,textile, plaster, fiberglass, ceramic, etc., which may be pre-primed bywaterborne or solvent borne primers. The architectural substrate may bean interior wall of a building or residence. When applied to a substrateand dried to form a coating thereon, it has been found that the driedcoating containing both the self-crosslinkable core-shell particles andthe acrylic polymer along with the matting agent imparts stainresistance at low gloss levels.

EXAMPLES

The following examples are presented to demonstrate the generalprinciples of the invention. The invention should not be considered aslimited to the specific examples presented. All parts and percentages inthe examples are by weight unless otherwise indicated.

Base Formulation

Coating compositions were prepared according to the Base Formulation inTable 1 with different resin blends, keeping the total resin solidsconstant by weight. The grind ingredients were mixed using a high-speedCowles disperser at sufficient speed to create a vortex where the blademeets the materials. After addition of the matting agent, the grindprocess resumed for 20 minutes, followed by adding the letdowningredients using a conventional lab mixer and mixing for 30 minutesafter the last addition.

TABLE 1 Component Amount (g) Grind Water 100.0 PANGEL S9¹ 3.0 TYLOSE HX6000² YG4 2.0 DREWPLUS ™ T-4507³ 2.0 TAMOL ™ 731A⁴ 5.0 ZETASPERSE 179⁵6.0 MINEX 4⁶ 92.0 Letdown Water 71.0 ACRYSOL RM-2020 NPR⁷ 17.0 TRONOXCR-826S⁸ 387.0 DREWPLUS ™ T-4507³ 8.0 Resin blend 430.0 OPTIFILMenhancer 400⁹ 15.0 ACTICIDE MBS¹⁰ 1.2 ¹Magnesium silicate rheologymodifier, available from The Carey Company (Addison, IL).²Hydroxyethylcellulose rheology modifier, available from SETylose USA(Plaquemine, LA). ³Mineral oil defoamer, available from Ashland(Columbus, OH). ⁴Dispersant available from The Dow Chemical Company(Midland, MI). ⁵Nonionic surfactant, available from Evonik Industries AG(Essen, Germany). ⁶Aluminum silicate matting agent, available from TheCary Company (Addison, IL). ⁷Hydrophobically modified ethylene oxideurethane rheology modifier, available from The Dow Chemical Company(Midland, MI). ⁸Rutile titanium dioxide slurry, available from TronoxLimited (Stamford, CT). ⁹Coalescent, available from The Eastman ChemicalCompany (Kingsport, TN). ¹⁰Biocide, available from Thor Specialties,Inc. (Shelton, CT).

Examples 1-6 Synthesis of Core-Shell Particles Example 1

Part A: A polyurethane was first prepared by charging the followingcomponents in order into a four necked round bottom flask fitted with athermocouple, mechanical stirrer, and condenser: 56 grams methylmethacrylate, 90 grams of butyl acrylate, 10 grams trimethylol propane,12 grams of hydroxyethyl methacrylate (HEMA), 0.9 grams of2,6-di-tert-butyl 4-methyl phenol, 182 grams of FOMREZ 55-56 (hydroxylterminated saturated linear polyester polyol, commercially availablefrom Chemtura Corporation (Middlebury, Conn.)) and 35 grams of dimethyolpropionic acid (DMPA). The mixture was heated to 50° C. and held for 15minutes. After heating the mixture, 180 grams of isophorone diisocyanatewas charged into the flask over 10 minutes and mixed for 15 minutes.Next, 8.2 grams of butyl acrylate 1.3 g, triethylamine and 0.34 grams ofdibutyl tin dilaurate (DBTDL) was charged into the flask. Immediateexotherm was observed. After exotherm subsided, the mixture was heatedto 90° C. and held for 60 minutes. The mixture was then cooled to 70°C., and 80 grams methyl methacrylate and 19.8 grams of hexanedioldiacrylate were charged into the flask. The mixture was kept at 60° C.before being dispersed into water.

Part B: A latex comprising polyurethane-acrylic core-shell particles wasprepared by first charging the following components into a four neckedround bottom flask fitted with a thermocouple, mechanical stirrer, andcondenser: 450 grams of deionized water, 26 grams of diacetoneacrylamide and 7.5 grams of ethylenediamine. The mixture was heated to70° C. and held for 2 hours with an N₂ blanket. After heating themixture, 26.8 grams adipic dihydrazide, 18.8 grams dimethylethanolamine, 1.0 gram ethylenediamine and 500 grams of deionized waterwere charged into the flask and held at 50° C. for 15 minutes. Next, 520grams of the polyurethane prepared in part A was dispersed into theflask over 20 minutes and mixed for an additional 15 minutes. A mixtureof 0.5 gram of ammonium persulfate and 40 grams of deionized water wascharged into the flask. After exotherm, the mixture was then held at 60°C. for an additional hour. After being cooled to 40° C., 0.2 grams ofFOAMKILL 649 (non-silicone defoamer, commercially available fromCrucible Chemical Company (Greenville, S.C.)), 3.0 grams of ACTICIDE MBS(microbiocide formed of a mixture of 1,2-benzisothiazolin-3-one and2-methyl-4-isothiazolin-3-one, commercially available from Thor GmbH(Speyer, Germany)), and 5 grams of deionized water were charged andmixed for an additional 15 minutes. The resulting latex had a solidcontent of 36.6%.

Example 2

Part A: A polyurethane was first prepared by charging the followingcomponents in order into a four necked round bottom flask fitted with athermocouple, mechanical stirrer, and condenser: 69 grams methylmethacrylate, 77 grams of butyl acrylate, 10 grams trimethylol propane,8 grams of hydroxyethyl methacrylate (HEMA), 0.9 grams of2,6-di-tert-butyl 4-methyl phenol, 182 grams of FOMREZ 55-56 (hydroxylterminated saturated linear polyester polyol, commercially availablefrom Chemtura Corporation (Middlebury, Conn.)) and 35 grams of dimethyolpropionic acid (DMPA). The mixture was heated to 50° C. and held for 15minutes. After heating the mixture, 176 grams of isophorone diisocyanatewas charged into the flask over 10 minutes and mixed for 15 minutes.Next, 8.2 grams of butyl acrylate, 1.3 grams triethylamine and 0.34grams of dibutyl tin dilaurate (DBTDL) was charged into the flask.Immediate exotherm was observed. After exotherm subsided, the mixturewas heated to 90° C. and held for 60 minutes. The mixture was thencooled to 70° C., and 80 grams methyl methacrylate and 19.8 grams ofhexanediol diacrylate were charged into the flask. The mixture was keptat 60° C. before being dispersed into water.

Part B: A latex comprising polyurethane-acrylic core-shell particles wasprepared by first charging the following components into a four neckedround bottom flask fitted with a thermocouple, mechanical stirrer, andcondenser: 450 grams of deionized water, 26 grams of diacetoneacrylamide and 7.5 grams of ethylenediamine. The mixture was heated to70° C. and held for 2 hours with an N₂ blanket. After heating themixture, 26.8 grams adipic dihydrazide, 18.8 grams dimethylethanolamine, 1.2 grams ethylenediamine and 500 grams of deionized waterwere charged into the flask and held at 50° C. for 15 minutes. Next, 520grams of the polyurethane prepared in part A was dispersed into theflask over 20 minutes and mixed for an additional 15 minutes. A mixtureof 0.5 gram of ammonium persulfate and 40 grams of deionized water wascharged into the flask. After exotherm, the mixture was then held at 60°C. for an additional hour. After being cooled to 40° C., 0.2 grams ofFOAMKILL 649 (non-silicone defoamer, commercially available fromCrucible Chemical Company (Greenville, S.C.)), 3.0 grams of ACTICIDE MBS(microbiocide formed of a mixture of 1,2-benzisothiazolin-3-one and2-methyl-4-isothiazolin-3-one, commercially available from Thor GmbH(Speyer, Germany)), and 5 grams of deionized water were charged andmixed for an additional 15 minutes. The resulting latex had a solidcontent of 36.9%.

Example 3

Part A: A polyurethane was first prepared by charging the followingcomponents in order into a four necked round bottom flask fitted with athermocouple, mechanical stirrer, and condenser: 81 grams methylmethacrylate, 65 grams of butyl acrylate, 6 grams trimethylol propane, 6grams of hydroxyethyl methacrylate (HEMA), 0.9 grams of2,6-di-tert-butyl 4-methyl phenol, 182 grams of FOMREZ 55-56 (hydroxylterminated saturated linear polyester polyol, commercially availablefrom Chemtura Corporation (Middlebury, Conn.)) and 35 grams of dimethyolpropionic acid (DMPA). The mixture was heated to 50° C. and held for 15minutes. After heating the mixture, 162 grams of isophorone diisocyanatewas charged into the flask over 10 minutes and mixed for 15 minutes.Next, 8.2 grams of butyl acrylate, 1.3 grams triethylamine and 0.34grams of dibutyl tin dilaurate (DBTDL) was charged into the flask.Immediate exotherm was observed. After exotherm subsided, the mixturewas heated to 90° C. and held for 60 minutes. The mixture was thencooled to 70° C., and 80 grams methyl methacrylate and 19.8 grams ofhexanediol diacrylate were charged into the flask. The mixture was keptat 60° C. before being dispersed into water.

Part B: A latex comprising polyurethane-acrylic core-shell particles wasprepared by first charging the following components into a four neckedround bottom flask fitted with a thermocouple, mechanical stirrer, andcondenser: 450 grams of deionized water, 26 grams of diacetoneacrylamide and 7.5 grams of ethylenediamine. The mixture was heated to70° C. and held for 2 hours with an N₂ blanket. After heating themixture, 26.8 grams adipic dihydrazide, 18.8 grams dimethyl ethanolamineand 500 grams of deionized water were charged into the flask and held at50° C. for 15 minutes. Next, 520 grams of the polyurethane prepared inpart A was dispersed into the flask over 20 minutes and mixed for anadditional 15 minutes. A mixture of 0.5 gram of ammonium persulfate and40 grams of deionized water was charged into the flask. After exotherm,the mixture was then held at 60° C. for an additional hour. After beingcooled to 40° C., 0.2 grams of FOAMKILL 649 (non-silicone defoamer,commercially available from Crucible Chemical Company (Greenville,S.C.)), 3.0 grams of ACTICIDE MBS (microbiocide formed of a mixture of1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one,commercially available from Thor GmbH (Speyer, Germany)), and 5 grams ofdeionized water were charged and mixed for an additional 15 minutes. Theresulting latex had a solid content of 36.7%.

Example 4

Part A: A polyurethane was first prepared by charging the followingcomponents in order into a four necked round bottom flask fitted with athermocouple, mechanical stirrer, and condenser: 93 grams methylmethacrylate, 53 grams of butyl acrylate, 5 grams trimethylol propane, 5grams of hydroxyethyl methacrylate (HEMA), 0.9 grams of2,6-di-tert-butyl 4-methyl phenol, 182 grams of FOMREZ 55-56 (hydroxylterminated saturated linear polyester polyol, commercially availablefrom Chemtura Corporation (Middlebury, Conn.)) and 35 grams of dimethyolpropionic acid (DMPA). The mixture was heated to 50° C. and held for 15minutes. After heating the mixture, 158 grams of isophorone diisocyanatewas charged into the flask over 10 minutes and mixed for 15 minutes.Next, 8.2 grams of butyl acrylate, 1.3 grams triethylamine and 0.34grams of dibutyl tin dilaurate (DBTDL) was charged into the flask.Immediate exotherm was observed. After exotherm subsided, the mixturewas heated to 90° C. and held for 60 minutes. The mixture was thencooled to 70° C., and 80 grams methyl methacrylate and 19.8 grams ofhexanediol diacrylate were charged into the flask. The mixture was keptat 60° C. before being dispersed into water.

Part B: A latex comprising polyurethane-acrylic core-shell particles wasprepared by first charging the following components into a four neckedround bottom flask fitted with a thermocouple, mechanical stirrer, andcondenser: 450 grams of deionized water, 26 grams of diacetoneacrylamide and 7.5 grams of ethylenediamine. The mixture was heated to70° C. and held for 2 hours with an N₂ blanket. After heating themixture, 26.8 grams adipic dihydrazide, 18.8 grams dimethyl ethanolamineand 500 grams of deionized water were charged into the flask and held at50° C. for 15 minutes. Next, 520 grams of the polyurethane prepared inpart A was dispersed into the flask over 20 minutes and mixed for anadditional 15 minutes. A mixture of 0.5 gram of ammonium persulfate and40 grams of deionized water was charged into the flask. After exotherm,the mixture was then held at 60° C. for an additional hour. After beingcooled to 40° C., 0.2 grams of FOAMKILL 649 (non-silicone defoamer,commercially available from Crucible Chemical Company (Greenville,S.C.)), 3.0 grams of ACTICIDE MBS (microbiocide formed of a mixture of1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one,commercially available from Thor GmbH (Speyer, Germany)), and 5 grams ofdeionized water were charged and mixed for an additional 15 minutes. Theresulting latex had a solid content of 37.7%.

Example 5

Part A: A polyurethane was first prepared by charging the followingcomponents in order into a four necked round bottom flask fitted with athermocouple, mechanical stirrer, and condenser: 69 grams methylmethacrylate, 77 grams of butyl acrylate, 16 g Silsurf A008up fromSiltech Corporation (Toronto, Canada), 10 grams trimethylol propane, 8grams of hydroxyethyl methacrylate (HEMA), 0.9 grams of2,6-di-tert-butyl 4-methyl phenol, 182 grams of FOMREZ 55-56 (hydroxylterminated saturated linear polyester polyol, commercially availablefrom Chemtura Corporation (Middlebury, Conn.)) and 35 grams of dimethyolpropionic acid (DMPA). The mixture was heated to 50° C. and held for 15minutes. After heating the mixture, 181 grams of isophorone diisocyanatewas charged into the flask over 10 minutes and mixed for 15 minutes.Next, 8.2 grams of butyl acrylate, 1.3 grams triethylamine and 0.34grams of dibutyl tin dilaurate (DBTDL) was charged into the flask.Immediate exotherm was observed. After exotherm subsided, the mixturewas heated to 90° C. and held for 60 minutes. The mixture was thencooled to 70° C., and 80 grams methyl methacrylate and 19.8 grams ofhexanediol diacrylate were charged into the flask. The mixture was keptat 60° C. before being dispersed into water.

Part B: A latex comprising polyurethane-acrylic core-shell particles wasprepared by first charging the following components into a four neckedround bottom flask fitted with a thermocouple, mechanical stirrer, andcondenser: 450 grams of deionized water, 26 grams of diacetoneacrylamide and 7.5 grams of ethylenediamine. The mixture was heated to70° C. and held for 2 hours with an N₂ blanket. After heating themixture, 26.8 grams adipic dihydrazide, 18.4 grams dimethyl ethanolamineand 500 grams of deionized water were charged into the flask and held at50° C. for 15 minutes. Next, 520 grams of the polyurethane prepared inpart A was dispersed into the flask over 20 minutes and mixed for anadditional 15 minutes. A mixture of 0.5 gram of ammonium persulfate and40 grams of deionized water was charged into the flask. After exotherm,the mixture was then held at 60° C. for an additional hour. After beingcooled to 40° C., 0.2 grams of FOAMKILL 649 (non-silicone defoamer,commercially available from Crucible Chemical Company (Greenville,S.C.)), 3.0 grams of ACTICIDE MBS (microbiocide formed of a mixture of1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one,commercially available from Thor GmbH (Speyer, Germany)), and 5 grams ofdeionized water were charged and mixed for an additional 15 minutes. Theresulting latex had a solid content of 36.3%.

Example 6

Part A: A polyurethane was first prepared by charging the followingcomponents in order into a four necked round bottom flask fitted with athermocouple, mechanical stirrer, and condenser: 69 grams methylmethacrylate, 77 grams of butyl acrylate, 16 grams Capstone AL62 (alinear telomere alcohol, including six perfluorinated carbon atoms andtwo nonfluorinated carbon atoms) from The Chemours Company (Wilmington,Del.), 10 grams trimethylol propane, 8 grams of hydroxyethylmethacrylate (HEMA), 0.9 grams of 2,6-di-tert-butyl 4-methyl phenol, 182grams of FOMREZ 55-56 (hydroxyl terminated saturated linear polyesterpolyol, commercially available from Chemtura Corporation (Middlebury,Conn.)) and 35 grams of dimethyol propionic acid (DMPA). The mixture washeated to 50° C. and held for 15 minutes. After heating the mixture, 184grams of isophorone diisocyanate was charged into the flask over 10minutes and mixed for 15 minutes. Next, 8.2 grams of butyl acrylate, 1.3grams triethylamine and 0.34 grams of dibutyl tin dilaurate (DBTDL) wascharged into the flask. Immediate exotherm was observed. After exothermsubsided, the mixture was heated to 90° C. and held for 60 minutes. Themixture was then cooled to 70° C., and 80 grams methyl methacrylate and19.8 grams of hexanediol diacrylate were charged into the flask. Themixture was kept at 60° C. before being dispersed into water.

Part B: A latex comprising polyurethane-acrylic core-shell particles wasprepared by first charging the following components into a four neckedround bottom flask fitted with a thermocouple, mechanical stirrer, andcondenser: 450 grams of deionized water, 26 grams of diacetoneacrylamide and 7.5 grams of ethylenediamine. The mixture was heated to70° C. and held for 2 hours with an N₂ blanket. After heating themixture, 26.8 grams adipic dihydrazide, 1,1 grams ethylenediamine, 18.4grams dimethyl ethanolamine and 500 grams of deionized water werecharged into the flask and held at 50° C. for 15 minutes. Next, 520grams of the polyurethane prepared in part A was dispersed into theflask over 20 minutes and mixed for an additional 15 minutes. A mixtureof 0.5 gram of ammonium persulfate and 40 grams of deionized water wascharged into the flask. After exotherm, the mixture was then held at 60°C. for an additional hour. After being cooled to 40° C., 0.2 grams ofFOAMKILL 649 (non-silicone defoamer, commercially available fromCrucible Chemical Company (Greenville, S.C.)), 3.0 grams of ACTICIDE MBS(microbiocide formed of a mixture of 1,2-benzisothiazolin-3-one and2-methyl-4-isothiazolin-3-one, commercially available from Thor GmbH(Speyer, Germany)), and 5 grams of deionized water were charged andmixed for an additional 15 minutes. The resulting latex had a solidcontent of 36.3%.

Examples 7-13 Stain Resistance Testing

The self-crosslinking polyurethane acrylate resins in Examples 1-6 wereblended at 33% based on total resin solids with a Base Acrylic latex,RHOPLEX SG-30, available from The Dow Chemical Company (Midland, Mich.),as the “Resin Blend” in Table 1 in the Base Formulation to form thecoating compositions for Examples 8-13, respectively, shown in Table 2.The coating composition of Comparative Example 7 is the Base Formulationwith the “Resin Blend” in Table 1 being RHOPLEX SG-30.

Coatings obtained from the coating compositions for Examples 7-13 weresubjected to stain resistance testing as described hereinafter.

The stain resistance test method is a more challenging, modified versionof ASTM D4828 to target stain removal using fewer scrub cycles.Substrates were prepared by drawing down the coating compositions ofExamples 7-13 onto black Leneta scrub panels (Form P121-10N) using a7-mil horseshoe drawdown bar. The coating compositions were dried atambient conditions for 7 days to form a cured coating, and then a stainswere applied. The following stains were applied to the coatings viaone-inch strips of filter paper saturated with the following fluids: redwine, grape juice, java concentrate, and hot coffee (70° C.). Thefollowing stains were directly applied to the coatings: mustard, redlipstick, green crayon, graphite powder, and Leneta staining mediumST-1. After 30 minutes, the lipstick and Leneta medium were wiped off,and the paint films were rinsed and placed in a washability machine(Gardner Abrasion Tester). A damp cellulosic sponge containing 10 gramsof water and 6 grams of SOFT SCRUB (cleanser, Henkel AG & Company, KGaA(Dusseldorf, Germany)) was placed in a 1000 grams holder, and the panelswere scrubbed for 6 cycles. After rinsing the panels and drying for atleast 2 hours, each of the 9 stains was rated on an integer scale of 0for no stain removal to 10 for complete stain removal. All stainresistance tests reported herein were run on the same day under the sameconditions by the same operator.

The results of the stain resistance testing are shown in Table 2.

TABLE 2 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Stain CE. 7 (Ex. 1) (Ex.2) (Ex. 3) (Ex. 4) (Ex. 5) (Ex. 6) Wine 1 4 5 5 4 5 4 Grape Juice 4 8 98 8 8 9 Java Concentrate 5 7 9 5 5 5 7 Hot Coffee 2 0 1 1 2 1 7 Mustard2 1 1 2 2 1 1 Lipstick 4 7 7 7 8 7 8 Green Crayon 9 9 9 9 9 9 9 Graphite6 7 8 6 6 6 8 Leneta Oil 5 6 7 6 6 4 6 Total 38 49 56 49 50 46 59 %Improvement — 29% 47% 29% 32% 21% 55%

Over 20% improvement in stain resistance was achieved using the coatingcompositions of Examples 8-13 compared to the coating composition ofComparative Example 7 (the Base Formulation with 100% RHOPLEX SG-30based on total resin solids). The highest improvement in stainresistance, up to 55%, was observed for the inventive resin containingfluoro functionality in the urethane shell (Example 6).

The present invention further includes the subject matter of thefollowing clauses:

Clause 1: A coating composition comprising: an aqueous dispersion ofself-crosslinkable core-shell particles, wherein the core-shellparticles comprise (1) a polymeric core at least partially encapsulatedby (2) a polymeric shell comprising urethane linkages, keto and/or aldofunctional groups, and hydrazide functional groups, wherein thepolymeric core is covalently bonded to at least a portion of thepolymeric shell, and an acrylic polymer, wherein the acrylic polymer isnon-reactive with the polymeric core and the polymeric shell.

Clause 2: The coating composition of clause 1, wherein the polymericcore comprises an addition polymer derived from ethylenicallyunsaturated monomers.

Clause 3: The coating composition of clause 2, wherein the ethylenicallyunsaturated monomers comprise a (meth)acrylate monomer, a vinyl monomer,and/or a combination thereof.

Clause 4: The coating composition of any of clauses 1-3, wherein thepolymeric shell comprises a water dispersible group.

Clause 5: The coating composition of any of clauses 1-4, wherein thecore-shell particles are formed from a mixture of reactants comprising:(a) isocyanate-functional ethylenically unsaturated polyurethaneprepolymers; (b) a Michael addition reaction product of ethylenicallyunsaturated monomers comprising a keto and/or aldo functional group, anda compound comprising at least two amino groups; (c) a hydrazidefunctional component; and (d) ethylenically unsaturated monomers.

Clause 6: The coating composition of any of clauses 1-5, wherein thepolymeric core is completely free of keto and/or aldo functional groups.

Clause 7: The coating composition of any of clauses 1-6, wherein theacrylic polymer is added to the aqueous dispersion after formation ofthe core-shell particles.

Clause 8: The coating composition of any of clauses 1-7, comprising10-50 wt % of the core-shell particles and 50-90 wt % of the acrylicpolymer, based on total resin solids.

Clause 9: The coating composition of any of clauses 1-8, wherein theself-crosslinkable core-shell particles further comprise afluorine-containing group and/or a silicon-containing group bonded tothe polymeric shell.

Clause 10: The coating composition of any of clauses 1-9, wherein thepolymeric core comprises a Tg of 0° C. to 50° C.

Clause 11: The coating composition of any of clauses 1-10, furthercomprising a rheology modifier.

Clause 12: The coating composition of any of clauses 1-11, furthercomprising a matting agent.

Clause 13: The coating composition of clause 12, wherein the coatingcomposition comprises an effective amount of the matting agent such thatwhen the coating composition is applied to a substrate and dried to forma coating, the coating exhibits a 60° gloss below 20 units and a 85°sheen below 35 units.

Clause 14: The coating composition of any of clauses 1-13, furthercomprising an inorganic pigment and/or filler.

Clause 15: The coating composition of any of clauses 1-14, wherein whenthe coating composition is applied to a substrate and dried to form acoating, the coating exhibits an improved stain resistance compared tothe same coating composition not including the core-shell particles.

Clause 16: A substrate at least partially coated with a coating formedfrom the coating composition of any of clauses 1-15.

Clause 17: The substrate of clause 16, wherein the substrate comprisesan architectural component.

Clause 18: The substrate of clause 16 or 17, wherein the substrate isnon-metallic.

Clause 19: A method of improving stain resistance of a substratecomprising: preparing a coating composition by: preparing an aqueousdispersion of self-crosslinkable core-shell particles dispersed in anaqueous medium, wherein the core-shell particles comprise (1) apolymeric core at least partially encapsulated by (2) a polymeric shellcomprising urethane linkages, keto and/or aldo functional groups, andhydrazide functional groups wherein the polymeric core is covalentlybonded to at least a portion of the polymeric shell; and adding anacrylic polymer to the aqueous dispersion, wherein the acrylic polymeris non-reactive with the polymeric core and the polymeric shell; andapplying the coating composition to a substrate.

Clause 20: The method of clause 19, wherein the acrylic polymer is addedto the aqueous dispersion after formation of the core-shell particles.

Clause 21: The method of clause 19 or 20, wherein the coatingcomposition comprises 10-50 wt % of the core-shell particles and 50-90wt % of the acrylic polymer, based on total resin solids.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

The invention claimed is:
 1. A coating composition comprising: anaqueous dispersion of self-crosslinkable core-shell particles, whereinthe core-shell particles comprise (1) a polymeric core at leastpartially encapsulated by (2) a polymeric shell comprising urethanelinkages, keto and/or aldo functional groups, and hydrazide functionalgroups, wherein the polymeric core is covalently bonded to at least aportion of the polymeric shell, and an acrylic polymer, wherein theacrylic polymer is non-reactive with the polymeric core and thepolymeric shell.
 2. The coating composition of claim 1, wherein thepolymeric core comprises an addition polymer derived from ethylenicallyunsaturated monomers.
 3. The coating composition of claim 2, wherein theethylenically unsaturated monomers comprise a (meth)acrylate monomer, avinyl monomer, and/or a combination thereof.
 4. The coating compositionof claim 1, wherein the polymeric shell comprises a water dispersiblegroup.
 5. The coating composition of claim 1, wherein the core-shellparticles are formed from a mixture of reactants comprising: (a)isocyanate-functional ethylenically unsaturated polyurethaneprepolymers; (b) a Michael addition reaction product of ethylenicallyunsaturated monomers comprising a keto and/or aldo functional group, anda compound comprising at least two amino groups; (c) a hydrazidefunctional component; and (d) ethylenically unsaturated monomers.
 6. Thecoating composition of claim 1, wherein the polymeric core is completelyfree of keto and/or aldo functional groups.
 7. The coating compositionof claim 1, wherein the acrylic polymer is added to the aqueousdispersion after formation of the core-shell particles.
 8. The coatingcomposition of claim 1, comprising 10-50 wt % of the core-shellparticles and 50-90 wt % of the acrylic polymer, based on total resinsolids.
 9. The coating composition of claim 1, wherein theself-crosslinkable core-shell particles further comprise afluorine-containing group and/or a silicon-containing group bonded tothe polymeric shell.
 10. The coating composition of claim 1, wherein thepolymeric core comprises a Tg of 0° C. to 50° C.
 11. The coatingcomposition of claim 1, further comprising a rheology modifier.
 12. Thecoating composition of claim 1, further comprising a matting agent. 13.The coating composition of claim 12, wherein the coating compositioncomprises an effective amount of the matting agent such that when thecoating composition is applied to a substrate and dried to form acoating, the coating exhibits a 60° gloss below 20 units and a 85° sheenbelow 35 units.
 14. The coating composition of claim 1, furthercomprising an inorganic pigment and/or filler.
 15. The coatingcomposition of claim 1, wherein when the coating composition is appliedto a substrate and dried to form a coating, the coating exhibits animproved stain resistance compared to the same coating composition notincluding the core-shell particles.
 16. A substrate at least partiallycoated with a coating formed from the coating composition of claim 1.17. The substrate of claim 16, wherein the substrate comprises anarchitectural component.
 18. The substrate of claim 16, wherein thesubstrate is non-metallic.
 19. A method of improving stain resistance ofa substrate comprising: preparing a coating composition by: preparing anaqueous dispersion of self-crosslinkable core-shell particles dispersedin an aqueous medium, wherein the core-shell particles comprise (1) apolymeric core at least partially encapsulated by (2) a polymeric shellcomprising urethane linkages, keto and/or aldo functional groups, andhydrazide functional groups wherein the polymeric core is covalentlybonded to at least a portion of the polymeric shell; and adding anacrylic polymer to the aqueous dispersion, wherein the acrylic polymeris non-reactive with the polymeric core and the polymeric shell; andapplying the coating composition to a substrate.
 20. The method of claim19, wherein the acrylic polymer is added to the aqueous dispersion afterformation of the core-shell particles.
 21. The method of claim 19,wherein the coating composition comprises 10-50 wt % of the core-shellparticles and 50-90 wt % of the acrylic polymer, based on total resinsolids.